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margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li class="switchers"> <div class="language_switcher_placeholder"></div> <div class="version_switcher_placeholder"></div> </li> <li> </li> <li id="cpython-language-and-version"> <a href="../index.html">3.12.3 Documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="python.html" accesskey="U">Python Runtime Services</a> »</li> <li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code> — Future statement definitions</a></li> <li class="right"> <div class="inline-search" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" aria-label="Quick search" type="search" name="q" id="search-box" /> <input type="submit" value="Go" /> </form> </div> | </li> <li class="right"> <label class="theme-selector-label"> Theme <select class="theme-selector" oninput="activateTheme(this.value)"> <option value="auto" selected>Auto</option> <option value="light">Light</option> <option value="dark">Dark</option> </select> </label> |</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <section id="module-__future__"> <span id="future-future-statement-definitions"></span><h1><a class="reference internal" href="#module-__future__" title="__future__: Future statement definitions"><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code></a> — Future statement definitions<a class="headerlink" href="#module-__future__" title="Link to this heading">¶</a></h1> <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/__future__.py">Lib/__future__.py</a></p> <hr class="docutils" /> <p>Imports of the form <code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">__future__</span> <span class="pre">import</span> <span class="pre">feature</span></code> are called <a class="reference internal" href="../reference/simple_stmts.html#future"><span class="std std-ref">future statements</span></a>. These are special-cased by the Python compiler to allow the use of new Python features in modules containing the future statement before the release in which the feature becomes standard.</p> <p>While these future statements are given additional special meaning by the Python compiler, they are still executed like any other import statement and the <a class="reference internal" href="#module-__future__" title="__future__: Future statement definitions"><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code></a> exists and is handled by the import system the same way any other Python module would be. This design serves three purposes:</p> <ul class="simple"> <li><p>To avoid confusing existing tools that analyze import statements and expect to find the modules they’re importing.</p></li> <li><p>To document when incompatible changes were introduced, and when they will be — or were — made mandatory. This is a form of executable documentation, and can be inspected programmatically via importing <a class="reference internal" href="#module-__future__" title="__future__: Future statement definitions"><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code></a> and examining its contents.</p></li> <li><p>To ensure that <a class="reference internal" href="../reference/simple_stmts.html#future"><span class="std std-ref">future statements</span></a> run under releases prior to Python 2.1 at least yield runtime exceptions (the import of <a class="reference internal" href="#module-__future__" title="__future__: Future statement definitions"><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code></a> will fail, because there was no module of that name prior to 2.1).</p></li> </ul> <section id="module-contents"> <h2>Module Contents<a class="headerlink" href="#module-contents" title="Link to this heading">¶</a></h2> <p>No feature description will ever be deleted from <a class="reference internal" href="#module-__future__" title="__future__: Future statement definitions"><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code></a>. Since its introduction in Python 2.1 the following features have found their way into the language using this mechanism:</p> <table class="docutils align-default"> <thead> <tr class="row-odd"><th class="head"><p>feature</p></th> <th class="head"><p>optional in</p></th> <th class="head"><p>mandatory in</p></th> <th class="head"><p>effect</p></th> </tr> </thead> <tbody> <tr class="row-even"><td><p>nested_scopes</p></td> <td><p>2.1.0b1</p></td> <td><p>2.2</p></td> <td><p><span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-0227/"><strong>PEP 227</strong></a>: <em>Statically Nested Scopes</em></p></td> </tr> <tr class="row-odd"><td><p>generators</p></td> <td><p>2.2.0a1</p></td> <td><p>2.3</p></td> <td><p><span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-0255/"><strong>PEP 255</strong></a>: <em>Simple Generators</em></p></td> </tr> <tr class="row-even"><td><p>division</p></td> <td><p>2.2.0a2</p></td> <td><p>3.0</p></td> <td><p><span class="target" id="index-2"></span><a class="pep reference external" href="https://peps.python.org/pep-0238/"><strong>PEP 238</strong></a>: <em>Changing the Division Operator</em></p></td> </tr> <tr class="row-odd"><td><p>absolute_import</p></td> <td><p>2.5.0a1</p></td> <td><p>3.0</p></td> <td><p><span class="target" id="index-3"></span><a class="pep reference external" href="https://peps.python.org/pep-0328/"><strong>PEP 328</strong></a>: <em>Imports: Multi-Line and Absolute/Relative</em></p></td> </tr> <tr class="row-even"><td><p>with_statement</p></td> <td><p>2.5.0a1</p></td> <td><p>2.6</p></td> <td><p><span class="target" id="index-4"></span><a class="pep reference external" href="https://peps.python.org/pep-0343/"><strong>PEP 343</strong></a>: <em>The “with” Statement</em></p></td> </tr> <tr class="row-odd"><td><p>print_function</p></td> <td><p>2.6.0a2</p></td> <td><p>3.0</p></td> <td><p><span class="target" id="index-5"></span><a class="pep reference external" href="https://peps.python.org/pep-3105/"><strong>PEP 3105</strong></a>: <em>Make print a function</em></p></td> </tr> <tr class="row-even"><td><p>unicode_literals</p></td> <td><p>2.6.0a2</p></td> <td><p>3.0</p></td> <td><p><span class="target" id="index-6"></span><a class="pep reference external" href="https://peps.python.org/pep-3112/"><strong>PEP 3112</strong></a>: <em>Bytes literals in Python 3000</em></p></td> </tr> <tr class="row-odd"><td><p>generator_stop</p></td> <td><p>3.5.0b1</p></td> <td><p>3.7</p></td> <td><p><span class="target" id="index-7"></span><a class="pep reference external" href="https://peps.python.org/pep-0479/"><strong>PEP 479</strong></a>: <em>StopIteration handling inside generators</em></p></td> </tr> <tr class="row-even"><td><p>annotations</p></td> <td><p>3.7.0b1</p></td> <td><p>TBD <a class="footnote-reference brackets" href="#id2" id="id1" role="doc-noteref"><span class="fn-bracket">[</span>1<span class="fn-bracket">]</span></a></p></td> <td><p><span class="target" id="index-8"></span><a class="pep reference external" href="https://peps.python.org/pep-0563/"><strong>PEP 563</strong></a>: <em>Postponed evaluation of annotations</em></p></td> </tr> </tbody> </table> <dl class="py class" id="future-classes"> <dt class="sig sig-object py" id="future__._Feature"> <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">_Feature</span></span><a class="headerlink" href="#future__._Feature" title="Link to this definition">¶</a></dt> <dd><p>Each statement in <code class="file docutils literal notranslate"><span class="pre">__future__.py</span></code> is of the form:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">FeatureName</span> <span class="o">=</span> <span class="n">_Feature</span><span class="p">(</span><span class="n">OptionalRelease</span><span class="p">,</span> <span class="n">MandatoryRelease</span><span class="p">,</span> <span class="n">CompilerFlag</span><span class="p">)</span> </pre></div> </div> <p>where, normally, <em>OptionalRelease</em> is less than <em>MandatoryRelease</em>, and both are 5-tuples of the same form as <a class="reference internal" href="sys.html#sys.version_info" title="sys.version_info"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.version_info</span></code></a>:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">PY_MAJOR_VERSION</span><span class="p">,</span> <span class="c1"># the 2 in 2.1.0a3; an int</span> <span class="n">PY_MINOR_VERSION</span><span class="p">,</span> <span class="c1"># the 1; an int</span> <span class="n">PY_MICRO_VERSION</span><span class="p">,</span> <span class="c1"># the 0; an int</span> <span class="n">PY_RELEASE_LEVEL</span><span class="p">,</span> <span class="c1"># "alpha", "beta", "candidate" or "final"; string</span> <span class="n">PY_RELEASE_SERIAL</span> <span class="c1"># the 3; an int</span> <span class="p">)</span> </pre></div> </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="future__._Feature.getOptionalRelease"> <span class="sig-prename descclassname"><span class="pre">_Feature.</span></span><span class="sig-name descname"><span class="pre">getOptionalRelease</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#future__._Feature.getOptionalRelease" title="Link to this definition">¶</a></dt> <dd><p><em>OptionalRelease</em> records the first release in which the feature was accepted.</p> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="future__._Feature.getMandatoryRelease"> <span class="sig-prename descclassname"><span class="pre">_Feature.</span></span><span class="sig-name descname"><span class="pre">getMandatoryRelease</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#future__._Feature.getMandatoryRelease" title="Link to this definition">¶</a></dt> <dd><p>In the case of a <em>MandatoryRelease</em> that has not yet occurred, <em>MandatoryRelease</em> predicts the release in which the feature will become part of the language.</p> <p>Else <em>MandatoryRelease</em> records when the feature became part of the language; in releases at or after that, modules no longer need a future statement to use the feature in question, but may continue to use such imports.</p> <p><em>MandatoryRelease</em> may also be <code class="docutils literal notranslate"><span class="pre">None</span></code>, meaning that a planned feature got dropped or that it is not yet decided.</p> </dd></dl> <dl class="py attribute"> <dt class="sig sig-object py" id="future__._Feature.compiler_flag"> <span class="sig-prename descclassname"><span class="pre">_Feature.</span></span><span class="sig-name descname"><span class="pre">compiler_flag</span></span><a class="headerlink" href="#future__._Feature.compiler_flag" title="Link to this definition">¶</a></dt> <dd><p><em>CompilerFlag</em> is the (bitfield) flag that should be passed in the fourth argument to the built-in function <a class="reference internal" href="functions.html#compile" title="compile"><code class="xref py py-func docutils literal notranslate"><span class="pre">compile()</span></code></a> to enable the feature in dynamically compiled code. This flag is stored in the <a class="reference internal" href="#future__._Feature.compiler_flag" title="__future__._Feature.compiler_flag"><code class="xref py py-attr docutils literal notranslate"><span class="pre">_Feature.compiler_flag</span></code></a> attribute on <a class="reference internal" href="#future__._Feature" title="__future__._Feature"><code class="xref py py-class docutils literal notranslate"><span class="pre">_Feature</span></code></a> instances.</p> </dd></dl> <aside class="footnote-list brackets"> <aside class="footnote brackets" id="id2" role="doc-footnote"> <span class="label"><span class="fn-bracket">[</span><a role="doc-backlink" href="#id1">1</a><span class="fn-bracket">]</span></span> <p><code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">__future__</span> <span class="pre">import</span> <span class="pre">annotations</span></code> was previously scheduled to become mandatory in Python 3.10, but the Python Steering Council twice decided to delay the change (<a class="reference external" href="https://mail.python.org/archives/list/python-dev@python.org/message/CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ/">announcement for Python 3.10</a>; <a class="reference external" href="https://mail.python.org/archives/list/python-dev@python.org/message/VIZEBX5EYMSYIJNDBF6DMUMZOCWHARSO/">announcement for Python 3.11</a>). No final decision has been made yet. See also <span class="target" id="index-9"></span><a class="pep reference external" href="https://peps.python.org/pep-0563/"><strong>PEP 563</strong></a> and <span class="target" id="index-10"></span><a class="pep reference external" href="https://peps.python.org/pep-0649/"><strong>PEP 649</strong></a>.</p> </aside> </aside> <div class="admonition seealso"> <p class="admonition-title">See also</p> <dl class="simple"> <dt><a class="reference internal" href="../reference/simple_stmts.html#future"><span class="std std-ref">Future statements</span></a></dt><dd><p>How the compiler treats future imports.</p> </dd> <dt><span class="target" id="index-11"></span><a class="pep reference external" href="https://peps.python.org/pep-0236/"><strong>PEP 236</strong></a> - Back to the __future__</dt><dd><p>The original proposal for the __future__ mechanism.</p> </dd> </dl> </div> </section> </section> <div class="clearer"></div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <div> <h3><a href="../contents.html">Table of Contents</a></h3> <ul> <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code> — Future statement definitions</a><ul> <li><a class="reference internal" href="#module-contents">Module Contents</a></li> </ul> </li> </ul> </div> <div> <h4>Previous topic</h4> <p class="topless"><a href="traceback.html" title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">traceback</span></code> — Print or retrieve a stack traceback</a></p> </div> <div> <h4>Next topic</h4> <p class="topless"><a href="gc.html" title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">gc</span></code> — Garbage Collector interface</a></p> </div> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li> <a href="https://github.com/python/cpython/blob/main/Doc/library/__future__.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </div> <div id="sidebarbutton" title="Collapse sidebar"> <span>«</span> </div> </div> <div class="clearer"></div> </div> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="gc.html" title="gc — Garbage Collector interface" >next</a> |</li> <li class="right" > <a href="traceback.html" title="traceback — Print or retrieve a stack traceback" >previous</a> |</li> <li><img src="../_static/py.svg" alt="Python logo" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li class="switchers"> <div class="language_switcher_placeholder"></div> <div class="version_switcher_placeholder"></div> </li> <li> </li> <li id="cpython-language-and-version"> <a href="../index.html">3.12.3 Documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="python.html" >Python Runtime Services</a> »</li> <li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code> — Future statement definitions</a></li> <li class="right"> <div class="inline-search" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" aria-label="Quick search" type="search" name="q" id="search-box" /> <input type="submit" value="Go" /> </form> </div> | </li> <li class="right"> <label class="theme-selector-label"> Theme <select class="theme-selector" oninput="activateTheme(this.value)"> <option value="auto" selected>Auto</option> <option value="light">Light</option> <option value="dark">Dark</option> </select> </label> |</li> </ul> </div> <div class="footer"> © <a href="../copyright.html"> Copyright </a> 2001-2024, Python Software Foundation. <br /> This page is licensed under the Python Software Foundation License Version 2. <br /> Examples, recipes, and other code in the documentation are additionally licensed under the Zero Clause BSD License. <br /> See <a href="/license.html">History and License</a> for more information.<br /> <br /> The Python Software Foundation is a non-profit corporation. <a href="https://www.python.org/psf/donations/">Please donate.</a> <br /> <br /> Last updated on Apr 09, 2024 (13:47 UTC). <a href="/bugs.html">Found a bug</a>? <br /> Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 7.2.6. </div> </body> </html>
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